Toward direct light-to-digital conversion using a pulse-driven hybrid MOS-PN photodetector

Area of Science:

• Solid-state physics
• Integrated circuit design
• Photonics

Background:

• Traditional imaging sensors often require complex analog-to-digital or time-to-digital conversion stages.
• These conversion processes can increase sensor complexity, area, and power consumption.
• Reducing dark levels is crucial for improving signal-to-noise ratio in photodetectors.

Purpose of the Study:

• To present a direct light-to-digital converter that bypasses traditional conversion methods.
• To enable a new generation of digital imaging sensors with enhanced efficiency.
• To investigate the impact of pulsed voltage operation on photodetector performance and dark level reduction.

Main Methods:

• Development of a direct light-to-digital converter utilizing a Metal-Oxide-Semiconductor (MOS) PN photodetector.
• Implementation of a pulsed voltage driving scheme for the photodetector.
• Validation through theoretical analysis and Technology Computer-Aided Design (TCAD) simulations.
• Fabrication of a prototype in 0.18 μm CMOS technology.

Main Results:

• The pulsed voltage operation significantly reduces the dark level of the photodetector.
• Experimental results demonstrate a substantial improvement in light sensitivity, by several orders of magnitude.
• The direct conversion approach successfully avoids analog-to-digital and time-to-digital conversion.

Conclusions:

• The presented direct light-to-digital converter offers a simplified and more efficient approach to digital imaging.
• Pulsed voltage operation is a key factor in enhancing photodetector sensitivity and reducing dark current.
• This technology paves the way for next-generation, low-complexity, low-power digital imaging sensors.